ABSTRACT
The Naore village, Shuang’an Town in the Ziyang County, southern Shaanxi, is one of the few known selenium (Se)-enriched areas in China, and in these locations, the early cases of human Se poisoning were recorded in the 1980’s. The Se source in soil is attributed to pyrite-bearing and Se-enriched tuffs and carbonaceous rocks of Lower Cambrian Lujiaping Formation. Selenium and arsenic (As) contents were analyzed by Hydride Generation-Atomic Fluorescence Spectrometry. Type-I pyrite is characterized by high Se and low As concentrations in the core and moderate Se and high As concentrations near the pyrite crystal margins. Type-II pyrite presents a similar distribution pattern of Se and As, being both poor at the core and Se-enriched along the edge. Pyrite is the major carrier for Se of Lujiaping Formation, and Se was incorporated mainly by isomorphic replacement. The texture of pyrite elemental zonations reflects multi-stage hydrothermal pulses with changing trace element concentrations.
